URL
https://opencores.org/ocsvn/openrisc/openrisc/trunk
Subversion Repositories openrisc
[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [gcc/] [ada/] [checks.ads] - Rev 729
Go to most recent revision | Compare with Previous | Blame | View Log
------------------------------------------------------------------------------ -- -- -- GNAT COMPILER COMPONENTS -- -- -- -- C H E C K S -- -- -- -- S p e c -- -- -- -- Copyright (C) 1992-2011, Free Software Foundation, Inc. -- -- -- -- GNAT is free software; you can redistribute it and/or modify it under -- -- terms of the GNU General Public License as published by the Free Soft- -- -- ware Foundation; either version 3, or (at your option) any later ver- -- -- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License -- -- for more details. You should have received a copy of the GNU General -- -- Public License distributed with GNAT; see file COPYING3. If not, go to -- -- http://www.gnu.org/licenses for a complete copy of the license. -- -- -- -- GNAT was originally developed by the GNAT team at New York University. -- -- Extensive contributions were provided by Ada Core Technologies Inc. -- -- -- ------------------------------------------------------------------------------ -- Package containing routines used to deal with runtime checks. These -- routines are used both by the semantics and by the expander. In some -- cases, checks are enabled simply by setting flags for gigi, and in -- other cases the code for the check is expanded. -- The approach used for range and length checks, in regards to suppressed -- checks, is to attempt to detect at compilation time that a constraint -- error will occur. If this is detected a warning or error is issued and the -- offending expression or statement replaced with a constraint error node. -- This always occurs whether checks are suppressed or not. Dynamic range -- checks are, of course, not inserted if checks are suppressed. with Namet; use Namet; with Table; with Types; use Types; with Uintp; use Uintp; package Checks is procedure Initialize; -- Called for each new main source program, to initialize internal -- variables used in the package body of the Checks unit. function Access_Checks_Suppressed (E : Entity_Id) return Boolean; function Accessibility_Checks_Suppressed (E : Entity_Id) return Boolean; function Alignment_Checks_Suppressed (E : Entity_Id) return Boolean; function Atomic_Synchronization_Disabled (E : Entity_Id) return Boolean; function Discriminant_Checks_Suppressed (E : Entity_Id) return Boolean; function Division_Checks_Suppressed (E : Entity_Id) return Boolean; function Elaboration_Checks_Suppressed (E : Entity_Id) return Boolean; function Index_Checks_Suppressed (E : Entity_Id) return Boolean; function Length_Checks_Suppressed (E : Entity_Id) return Boolean; function Overflow_Checks_Suppressed (E : Entity_Id) return Boolean; function Range_Checks_Suppressed (E : Entity_Id) return Boolean; function Storage_Checks_Suppressed (E : Entity_Id) return Boolean; function Tag_Checks_Suppressed (E : Entity_Id) return Boolean; function Validity_Checks_Suppressed (E : Entity_Id) return Boolean; -- These functions check to see if the named check is suppressed, either -- by an active scope suppress setting, or because the check has been -- specifically suppressed for the given entity. If no entity is relevant -- for the current check, then Empty is used as an argument. Note: the -- reason we insist on specifying Empty is to force the caller to think -- about whether there is any relevant entity that should be checked. ------------------------------------------- -- Procedures to Activate Checking Flags -- ------------------------------------------- procedure Activate_Division_Check (N : Node_Id); pragma Inline (Activate_Division_Check); -- Sets Do_Division_Check flag in node N, and handles possible local raise. -- Always call this routine rather than calling Set_Do_Division_Check to -- set an explicit value of True, to ensure handling the local raise case. procedure Activate_Overflow_Check (N : Node_Id); pragma Inline (Activate_Overflow_Check); -- Sets Do_Overflow_Check flag in node N, and handles possible local raise. -- Always call this routine rather than calling Set_Do_Overflow_Check to -- set an explicit value of True, to ensure handling the local raise case. procedure Activate_Range_Check (N : Node_Id); pragma Inline (Activate_Range_Check); -- Sets Do_Range_Check flag in node N, and handles possible local raise -- Always call this routine rather than calling Set_Do_Range_Check to -- set an explicit value of True, to ensure handling the local raise case. -------------------------------- -- Procedures to Apply Checks -- -------------------------------- -- General note on following checks. These checks are always active if -- Expander_Active and not Inside_A_Generic. They are inactive and have -- no effect Inside_A_Generic. In the case where not Expander_Active -- and not Inside_A_Generic, most of them are inactive, but some of them -- operate anyway since they may generate useful compile time warnings. procedure Apply_Access_Check (N : Node_Id); -- Determines whether an expression node requires a runtime access -- check and if so inserts the appropriate run-time check. procedure Apply_Accessibility_Check (N : Node_Id; Typ : Entity_Id; Insert_Node : Node_Id); -- Given a name N denoting an access parameter, emits a run-time -- accessibility check (if necessary), checking that the level of -- the object denoted by the access parameter is not deeper than the -- level of the type Typ. Program_Error is raised if the check fails. -- Insert_Node indicates the node where the check should be inserted. procedure Apply_Address_Clause_Check (E : Entity_Id; N : Node_Id); -- E is the entity for an object which has an address clause. If checks -- are enabled, then this procedure generates a check that the specified -- address has an alignment consistent with the alignment of the object, -- raising PE if this is not the case. The resulting check (if one is -- generated) is inserted before node N. check is also made for the case of -- a clear overlay situation that the size of the overlaying object is not -- larger than the overlaid object. procedure Apply_Arithmetic_Overflow_Check (N : Node_Id); -- Given a binary arithmetic operator (+ - *) expand a software integer -- overflow check using range checks on a larger checking type or a call -- to an appropriate runtime routine. This is used for all three operators -- for the signed integer case, and for +/- in the fixed-point case. The -- check is expanded only if Software_Overflow_Checking is enabled and -- Do_Overflow_Check is set on node N. Note that divide is handled -- separately using Apply_Arithmetic_Divide_Overflow_Check. procedure Apply_Constraint_Check (N : Node_Id; Typ : Entity_Id; No_Sliding : Boolean := False); -- Top-level procedure, calls all the others depending on the class of -- Typ. Checks that expression N satisfies the constraint of type Typ. -- No_Sliding is only relevant for constrained array types, if set to -- True, it checks that indexes are in range. procedure Apply_Discriminant_Check (N : Node_Id; Typ : Entity_Id; Lhs : Node_Id := Empty); -- Given an expression N of a discriminated type, or of an access type -- whose designated type is a discriminanted type, generates a check to -- ensure that the expression can be converted to the subtype given as -- the second parameter. Lhs is empty except in the case of assignments, -- where the target object may be needed to determine the subtype to -- check against (such as the cases of unconstrained formal parameters -- and unconstrained aliased objects). For the case of unconstrained -- formals, the check is performed only if the corresponding actual is -- constrained, i.e., whether Lhs'Constrained is True. procedure Apply_Predicate_Check (N : Node_Id; Typ : Entity_Id); -- N is an expression to which a predicate check may need to be applied -- for Typ, if Typ has a predicate function. The check is applied only -- if the type of N does not match Typ. function Build_Discriminant_Checks (N : Node_Id; T_Typ : Entity_Id) return Node_Id; -- Subsidiary routine for Apply_Discriminant_Check. Builds the expression -- that compares discriminants of the expression with discriminants of the -- type. Also used directly for membership tests (see Exp_Ch4.Expand_N_In). procedure Apply_Divide_Check (N : Node_Id); -- The node kind is N_Op_Divide, N_Op_Mod, or N_Op_Rem. An appropriate -- check is generated to ensure that the right operand is non-zero. In -- the divide case, we also check that we do not have the annoying case -- of the largest negative number divided by minus one. procedure Apply_Type_Conversion_Checks (N : Node_Id); -- N is an N_Type_Conversion node. A type conversion actually involves -- two sorts of checks. The first check is the checks that ensures that -- the operand in the type conversion fits onto the base type of the -- subtype it is being converted to (see RM 4.6 (28)-(50)). The second -- check is there to ensure that once the operand has been converted to -- a value of the target type, this converted value meets the -- constraints imposed by the target subtype (see RM 4.6 (51)). procedure Apply_Universal_Integer_Attribute_Checks (N : Node_Id); -- The argument N is an attribute reference node intended for processing -- by gigi. The attribute is one that returns a universal integer, but -- the attribute reference node is currently typed with the expected -- result type. This routine deals with range and overflow checks needed -- to make sure that the universal result is in range. procedure Determine_Range (N : Node_Id; OK : out Boolean; Lo : out Uint; Hi : out Uint; Assume_Valid : Boolean := False); -- N is a node for a subexpression. If N is of a discrete type with no -- error indications, and no other peculiarities (e.g. missing type -- fields), then OK is True on return, and Lo and Hi are set to a -- conservative estimate of the possible range of values of N. Thus if OK -- is True on return, the value of the subexpression N is known to like in -- the range Lo .. Hi (inclusive). If the expression is not of a discrete -- type, or some kind of error condition is detected, then OK is False on -- exit, and Lo/Hi are set to No_Uint. Thus the significance of OK being -- False on return is that no useful information is available on the range -- of the expression. Assume_Valid determines whether the processing is -- allowed to assume that values are in range of their subtypes. If it is -- set to True, then this assumption is valid, if False, then processing -- is done using base types to allow invalid values. procedure Install_Null_Excluding_Check (N : Node_Id); -- Determines whether an access node requires a runtime access check and -- if so inserts the appropriate run-time check. ------------------------------------------------------- -- Control and Optimization of Range/Overflow Checks -- ------------------------------------------------------- -- Range checks are controlled by the Do_Range_Check flag. The front end -- is responsible for setting this flag in relevant nodes. Originally -- the back end generated all corresponding range checks. But later on -- we decided to generate many range checks in the front end. We are now -- in the transitional phase where some of these checks are still done -- by the back end, but many are done by the front end. It is possible -- that in the future we might move all the checks to the front end. The -- main remaining back end checks are for subscript checking. -- Overflow checks are similarly controlled by the Do_Overflow_Check flag. -- The difference here is that if back end overflow checks are inactive -- (Backend_Overflow_Checks_On_Target set False), then the actual overflow -- checks are generated by the front end, but if back end overflow checks -- are active (Backend_Overflow_Checks_On_Target set True), then the back -- end does generate the checks. -- The following two routines are used to set these flags, they allow -- for the possibility of eliminating checks. Checks can be eliminated -- if an identical check has already been performed. procedure Enable_Overflow_Check (N : Node_Id); -- First this routine determines if an overflow check is needed by doing -- an appropriate range check. If a check is not needed, then the call -- has no effect. If a check is needed then this routine sets the flag -- Do_Overflow_Check in node N to True, unless it can be determined that -- the check is not needed. The only condition under which this is the -- case is if there was an identical check earlier on. procedure Enable_Range_Check (N : Node_Id); -- Set Do_Range_Check flag in node N True, unless it can be determined -- that the check is not needed. The only condition under which this is -- the case is if there was an identical check earlier on. This routine -- is not responsible for doing range analysis to determine whether or -- not such a check is needed -- the caller is expected to do this. The -- one other case in which the request to set the flag is ignored is -- when Kill_Range_Check is set in an N_Unchecked_Conversion node. -- The following routines are used to keep track of processing sequences -- of statements (e.g. the THEN statements of an IF statement). A check -- that appears within such a sequence can eliminate an identical check -- within this sequence of statements. However, after the end of the -- sequence of statements, such a check is no longer of interest, since -- it may not have been executed. procedure Conditional_Statements_Begin; -- This call marks the start of processing of a sequence of statements. -- Every call to this procedure must be followed by a matching call to -- Conditional_Statements_End. procedure Conditional_Statements_End; -- This call removes from consideration all saved checks since the -- corresponding call to Conditional_Statements_Begin. These two -- procedures operate in a stack like manner. -- The mechanism for optimizing checks works by remembering checks -- that have already been made, but certain conditions, for example -- an assignment to a variable involved in a check, may mean that the -- remembered check is no longer valid, in the sense that if the same -- expression appears again, another check is required because the -- value may have changed. -- The following routines are used to note conditions which may render -- some or all of the stored and remembered checks to be invalidated. procedure Kill_Checks (V : Entity_Id); -- This procedure records an assignment or other condition that causes -- the value of the variable to be changed, invalidating any stored -- checks that reference the value. Note that all such checks must -- be discarded, even if they are not in the current statement range. procedure Kill_All_Checks; -- This procedure kills all remembered checks ----------------------------- -- Length and Range Checks -- ----------------------------- -- In the following procedures, there are three arguments which have -- a common meaning as follows: -- Expr The expression to be checked. If a check is required, -- the appropriate flag will be placed on this node. Whether -- this node is further examined depends on the setting of -- the parameter Source_Typ, as described below. -- ??? Apply_Length_Check and Apply_Range_Check do not have an Expr -- formal -- ??? Apply_Length_Check and Apply_Range_Check have a Ck_Node formal -- which is undocumented, is it the same as Expr? -- Target_Typ The target type on which the check is to be based. For -- example, if we have a scalar range check, then the check -- is that we are in range of this type. -- Source_Typ Normally Empty, but can be set to a type, in which case -- this type is used for the check, see below. -- The checks operate in one of two modes: -- If Source_Typ is Empty, then the node Expr is examined, at the very -- least to get the source subtype. In addition for some of the checks, -- the actual form of the node may be examined. For example, a node of -- type Integer whose actual form is an Integer conversion from a type -- with range 0 .. 3 can be determined to have a value in range 0 .. 3. -- If Source_Typ is given, then nothing can be assumed about the Expr, -- and indeed its contents are not examined. In this case the check is -- based on the assumption that Expr can be an arbitrary value of the -- given Source_Typ. -- Currently, the only case in which a Source_Typ is explicitly supplied -- is for the case of Out and In_Out parameters, where, for the conversion -- on return (the Out direction), the types must be reversed. This is -- handled by the caller. procedure Apply_Length_Check (Ck_Node : Node_Id; Target_Typ : Entity_Id; Source_Typ : Entity_Id := Empty); -- This procedure builds a sequence of declarations to do a length check -- that checks if the lengths of the two arrays Target_Typ and source type -- are the same. The resulting actions are inserted at Node using a call -- to Insert_Actions. -- -- For access types, the Directly_Designated_Type is retrieved and -- processing continues as enumerated above, with a guard against null -- values. -- -- Note: calls to Apply_Length_Check currently never supply an explicit -- Source_Typ parameter, but Apply_Length_Check takes this parameter and -- processes it as described above for consistency with the other routines -- in this section. procedure Apply_Range_Check (Ck_Node : Node_Id; Target_Typ : Entity_Id; Source_Typ : Entity_Id := Empty); -- For a Node of kind N_Range, constructs a range check action that tests -- first that the range is not null and then that the range is contained in -- the Target_Typ range. -- -- For scalar types, constructs a range check action that first tests that -- the expression is contained in the Target_Typ range. The difference -- between this and Apply_Scalar_Range_Check is that the latter generates -- the actual checking code in gigi against the Etype of the expression. -- -- For constrained array types, construct series of range check actions -- to check that each Expr range is properly contained in the range of -- Target_Typ. -- -- For a type conversion to an unconstrained array type, constructs a range -- check action to check that the bounds of the source type are within the -- constraints imposed by the Target_Typ. -- -- For access types, the Directly_Designated_Type is retrieved and -- processing continues as enumerated above, with a guard against null -- values. -- -- The source type is used by type conversions to unconstrained array -- types to retrieve the corresponding bounds. procedure Apply_Static_Length_Check (Expr : Node_Id; Target_Typ : Entity_Id; Source_Typ : Entity_Id := Empty); -- Tries to determine statically whether the two array types source type -- and Target_Typ have the same length. If it can be determined at compile -- time that they do not, then an N_Raise_Constraint_Error node replaces -- Expr, and a warning message is issued. procedure Apply_Scalar_Range_Check (Expr : Node_Id; Target_Typ : Entity_Id; Source_Typ : Entity_Id := Empty; Fixed_Int : Boolean := False); -- For scalar types, determines whether an expression node should be -- flagged as needing a runtime range check. If the node requires such a -- check, the Do_Range_Check flag is turned on. The Fixed_Int flag if set -- causes any fixed-point values to be treated as though they were discrete -- values (i.e. the underlying integer value is used). type Check_Result is private; -- Type used to return result of Get_Range_Checks call, for later use in -- call to Insert_Range_Checks procedure. function Get_Range_Checks (Ck_Node : Node_Id; Target_Typ : Entity_Id; Source_Typ : Entity_Id := Empty; Warn_Node : Node_Id := Empty) return Check_Result; -- Like Apply_Range_Check, except it does not modify anything. Instead -- it returns an encapsulated result of the check operations for later -- use in a call to Insert_Range_Checks. If Warn_Node is non-empty, its -- Sloc is used, in the static case, for the generated warning or error. -- Additionally, it is used rather than Expr (or Low/High_Bound of Expr) -- in constructing the check. procedure Append_Range_Checks (Checks : Check_Result; Stmts : List_Id; Suppress_Typ : Entity_Id; Static_Sloc : Source_Ptr; Flag_Node : Node_Id); -- Called to append range checks as returned by a call to Get_Range_Checks. -- Stmts is a list to which either the dynamic check is appended or the -- raise Constraint_Error statement is appended (for static checks). -- Static_Sloc is the Sloc at which the raise CE node points, Flag_Node is -- used as the node at which to set the Has_Dynamic_Check flag. Checks_On -- is a boolean value that says if range and index checking is on or not. procedure Insert_Range_Checks (Checks : Check_Result; Node : Node_Id; Suppress_Typ : Entity_Id; Static_Sloc : Source_Ptr := No_Location; Flag_Node : Node_Id := Empty; Do_Before : Boolean := False); -- Called to insert range checks as returned by a call to Get_Range_Checks. -- Node is the node after which either the dynamic check is inserted or -- the raise Constraint_Error statement is inserted (for static checks). -- Suppress_Typ is the type to check to determine if checks are suppressed. -- Static_Sloc, if passed, is the Sloc at which the raise CE node points, -- otherwise Sloc (Node) is used. The Has_Dynamic_Check flag is normally -- set at Node. If Flag_Node is present, then this is used instead as the -- node at which to set the Has_Dynamic_Check flag. Normally the check is -- inserted after, if Do_Before is True, the check is inserted before -- Node. ----------------------- -- Expander Routines -- ----------------------- -- Some of the earlier processing for checks results in temporarily setting -- the Do_Range_Check flag rather than actually generating checks. Now we -- are moving the generation of such checks into the front end for reasons -- of efficiency and simplicity (there were difficulties in handling this -- in the back end when side effects were present in the expressions being -- checked). -- Probably we could eliminate the Do_Range_Check flag entirely and -- generate the checks earlier, but this is a delicate area and it -- seemed safer to implement the following routines, which are called -- late on in the expansion process. They check the Do_Range_Check flag -- and if it is set, generate the actual checks and reset the flag. procedure Generate_Range_Check (N : Node_Id; Target_Type : Entity_Id; Reason : RT_Exception_Code); -- This procedure is called to actually generate and insert a range check. -- A check is generated to ensure that the value of N lies within the range -- of the target type. Note that the base type of N may be different from -- the base type of the target type. This happens in the conversion case. -- The Reason parameter is the exception code to be used for the exception -- if raised. -- -- Note on the relation of this routine to the Do_Range_Check flag. Mostly -- for historical reasons, we often set the Do_Range_Check flag and then -- later we call Generate_Range_Check if this flag is set. Most probably we -- could eliminate this intermediate setting of the flag (historically the -- back end dealt with range checks, using this flag to indicate if a check -- was required, then we moved checks into the front end). procedure Generate_Index_Checks (N : Node_Id); -- This procedure is called to generate index checks on the subscripts for -- the indexed component node N. Each subscript expression is examined, and -- if the Do_Range_Check flag is set, an appropriate index check is -- generated and the flag is reset. -- Similarly, we set the flag Do_Discriminant_Check in the semantic -- analysis to indicate that a discriminant check is required for selected -- component of a discriminated type. The following routine is called from -- the expander to actually generate the call. procedure Generate_Discriminant_Check (N : Node_Id); -- N is a selected component for which a discriminant check is required to -- make sure that the discriminants have appropriate values for the -- selection. This is done by calling the appropriate discriminant checking -- routine for the selector. ----------------------- -- Validity Checking -- ----------------------- -- In (RM 13.9.1(9-11)) we have the following rules on invalid values -- If the representation of a scalar object does not represent value of -- the object's subtype (perhaps because the object was not initialized), -- the object is said to have an invalid representation. It is a bounded -- error to evaluate the value of such an object. If the error is -- detected, either Constraint_Error or Program_Error is raised. -- Otherwise, execution continues using the invalid representation. The -- rules of the language outside this subclause assume that all objects -- have valid representations. The semantics of operations on invalid -- representations are as follows: -- -- 10 If the representation of the object represents a value of the -- object's type, the value of the type is used. -- -- 11 If the representation of the object does not represent a value -- of the object's type, the semantics of operations on such -- representations is implementation-defined, but does not by -- itself lead to erroneous or unpredictable execution, or to -- other objects becoming abnormal. -- We quote the rules in full here since they are quite delicate. Most -- of the time, we can just compute away with wrong values, and get a -- possibly wrong result, which is well within the range of allowed -- implementation defined behavior. The two tricky cases are subscripted -- array assignments, where we don't want to do wild stores, and case -- statements where we don't want to do wild jumps. -- In GNAT, we control validity checking with a switch -gnatV that can take -- three parameters, n/d/f for None/Default/Full. These modes have the -- following meanings: -- None (no validity checking) -- In this mode, there is no specific checking for invalid values -- and the code generator assumes that all stored values are always -- within the bounds of the object subtype. The consequences are as -- follows: -- For case statements, an out of range invalid value will cause -- Constraint_Error to be raised, or an arbitrary one of the case -- alternatives will be executed. Wild jumps cannot result even -- in this mode, since we always do a range check -- For subscripted array assignments, wild stores will result in -- the expected manner when addresses are calculated using values -- of subscripts that are out of range. -- It could perhaps be argued that this mode is still conformant with -- the letter of the RM, since implementation defined is a rather -- broad category, but certainly it is not in the spirit of the -- RM requirement, since wild stores certainly seem to be a case of -- erroneous behavior. -- Default (default standard RM-compatible validity checking) -- In this mode, which is the default, minimal validity checking is -- performed to ensure no erroneous behavior as follows: -- For case statements, an out of range invalid value will cause -- Constraint_Error to be raised. -- For subscripted array assignments, invalid out of range -- subscript values will cause Constraint_Error to be raised. -- Full (Full validity checking) -- In this mode, the protections guaranteed by the standard mode are -- in place, and the following additional checks are made: -- For every assignment, the right side is checked for validity -- For every call, IN and IN OUT parameters are checked for validity -- For every subscripted array reference, both for stores and loads, -- all subscripts are checked for validity. -- These checks are not required by the RM, but will in practice -- improve the detection of uninitialized variables, particularly -- if used in conjunction with pragma Normalize_Scalars. -- In the above description, we talk about performing validity checks, -- but we don't actually generate a check in a case where the compiler -- can be sure that the value is valid. Note that this assurance must -- be achieved without assuming that any uninitialized value lies within -- the range of its type. The following are cases in which values are -- known to be valid. The flag Is_Known_Valid is used to keep track of -- some of these cases. -- If all possible stored values are valid, then any uninitialized -- value must be valid. -- Literals, including enumeration literals, are clearly always valid -- Constants are always assumed valid, with a validity check being -- performed on the initializing value where necessary to ensure that -- this is the case. -- For variables, the status is set to known valid if there is an -- initializing expression. Again a check is made on the initializing -- value if necessary to ensure that this assumption is valid. The -- status can change as a result of local assignments to a variable. -- If a known valid value is unconditionally assigned, then we mark -- the left side as known valid. If a value is assigned that is not -- known to be valid, then we mark the left side as invalid. This -- kind of processing does NOT apply to non-local variables since we -- are not following the flow graph (more properly the flow of actual -- processing only corresponds to the flow graph for local assignments). -- For non-local variables, we preserve the current setting, i.e. a -- validity check is performed when assigning to a knonwn valid global. -- Note: no validity checking is required if range checks are suppressed -- regardless of the setting of the validity checking mode. -- The following procedures are used in handling validity checking procedure Apply_Subscript_Validity_Checks (Expr : Node_Id); -- Expr is the node for an indexed component. If validity checking and -- range checking are enabled, all subscripts for this indexed component -- are checked for validity. procedure Check_Valid_Lvalue_Subscripts (Expr : Node_Id); -- Expr is a lvalue, i.e. an expression representing the target of an -- assignment. This procedure checks for this expression involving an -- assignment to an array value. We have to be sure that all the subscripts -- in such a case are valid, since according to the rules in (RM -- 13.9.1(9-11)) such assignments are not permitted to result in erroneous -- behavior in the case of invalid subscript values. procedure Ensure_Valid (Expr : Node_Id; Holes_OK : Boolean := False); -- Ensure that Expr represents a valid value of its type. If this type -- is not a scalar type, then the call has no effect, since validity -- is only an issue for scalar types. The effect of this call is to -- check if the value is known valid, if so, nothing needs to be done. -- If this is not known, then either Expr is set to be range checked, -- or specific checking code is inserted so that an exception is raised -- if the value is not valid. -- -- The optional argument Holes_OK indicates whether it is necessary to -- worry about enumeration types with non-standard representations leading -- to "holes" in the range of possible representations. If Holes_OK is -- True, then such values are assumed valid (this is used when the caller -- will make a separate check for this case anyway). If Holes_OK is False, -- then this case is checked, and code is inserted to ensure that Expr is -- valid, raising Constraint_Error if the value is not valid. function Expr_Known_Valid (Expr : Node_Id) return Boolean; -- This function tests it the value of Expr is known to be valid in the -- sense of RM 13.9.1(9-11). In the case of GNAT, it is only discrete types -- which are a concern, since for non-discrete types we simply continue -- computation with invalid values, which does not lead to erroneous -- behavior. Thus Expr_Known_Valid always returns True if the type of Expr -- is non-discrete. For discrete types the value returned is True only if -- it can be determined that the value is Valid. Otherwise False is -- returned. procedure Insert_Valid_Check (Expr : Node_Id); -- Inserts code that will check for the value of Expr being valid, in -- the sense of the 'Valid attribute returning True. Constraint_Error -- will be raised if the value is not valid. procedure Null_Exclusion_Static_Checks (N : Node_Id); -- Ada 2005 (AI-231): Check bad usages of the null-exclusion issue procedure Remove_Checks (Expr : Node_Id); -- Remove all checks from Expr except those that are only executed -- conditionally (on the right side of And Then/Or Else. This call -- removes only embedded checks (Do_Range_Check, Do_Overflow_Check). procedure Validity_Check_Range (N : Node_Id); -- If N is an N_Range node, then Ensure_Valid is called on its bounds, -- if validity checking of operands is enabled. ----------------------------- -- Handling of Check Names -- ----------------------------- -- The following table contains Name_Id's for recognized checks. The first -- entries (corresponding to the values of the subtype Predefined_Check_Id) -- contain the Name_Id values for the checks that are predefined, including -- All_Checks (see Types). Remaining entries are those that are introduced -- by pragma Check_Names. package Check_Names is new Table.Table ( Table_Component_Type => Name_Id, Table_Index_Type => Check_Id, Table_Low_Bound => 1, Table_Initial => 30, Table_Increment => 200, Table_Name => "Name_Check_Names"); function Get_Check_Id (N : Name_Id) return Check_Id; -- Function to search above table for matching name. If found returns the -- corresponding Check_Id value in the range 1 .. Check_Name.Last. If not -- found returns No_Check_Id. private type Check_Result is array (Positive range 1 .. 2) of Node_Id; -- There are two cases for the result returned by Range_Check: -- -- For the static case the result is one or two nodes that should cause -- a Constraint_Error. Typically these will include Expr itself or the -- direct descendents of Expr, such as Low/High_Bound (Expr)). It is the -- responsibility of the caller to rewrite and substitute the nodes with -- N_Raise_Constraint_Error nodes. -- -- For the non-static case a single N_Raise_Constraint_Error node with a -- non-empty Condition field is returned. -- -- Unused entries in Check_Result, if any, are simply set to Empty For -- external clients, the required processing on this result is achieved -- using the Insert_Range_Checks routine. pragma Inline (Apply_Length_Check); pragma Inline (Apply_Range_Check); pragma Inline (Apply_Static_Length_Check); end Checks;
Go to most recent revision | Compare with Previous | Blame | View Log